Excitability Gene Found Studies First To Associate Gene With Personality Trait

Scientists say they’ve identified a gene that influences how impulsive, excitable, quick-tempered and extravagant you are, a possible step toward unraveling the genetics of personality.

Two studies provide the first confirmed association between a particular gene and a normal personality trait - in this case, a characteristic scientists call “novelty-seeking” which includes impulsiveness, excitability and the like.

Previous studies have shown more generally that genes influence personality, as do life experiences.

As scientists discover more individual genes that affect particular traits, it might open the door to identifying people at risk for problems like drug abuse and counseling them on how to lower their risk, said researcher Richard Ebstein.

It might also add a twist to the issue of who’s entitled to know about a person’s genetic makeup.

An insurance company might want to know that “genetically you’re a thrill-seeker and enjoy jumping out of airplanes in a skydiving club, and taking risks in general,” said Ebstein, head of research at the Sarah Herzog Memorial Hospital in Jerusalem.

Ebstein is the lead author of one study of the gene in the January issue of the journal Nature Genetics. The second study reproduced Ebstein’s results in a different population.

“This is major news,” said psychologist Brian Gladue, who studies the biology of behavior at the Institute for Policy Research at the University of Cincinnati.

“This is going to open up a whole new field of molecular personality research,” he said.

The discovery provides “the first missing link” between genes and personality by implicating a particular communication system in the brain, Gladue said.

In that communication system, brain cells signal each other with a chemical messenger called dopamine. Dopamine is secreted by a signaling cells, and delivers its message by binding to receptors on the surface of receiving cells.

The gene identified in the study tells cells how to make one kind of dopamine receptor.

The studies found that, on average, people with a particular version of the gene score about 10 percent higher for novelty-seeking on personality tests than people who lack that version.

People who are above average on novelty-seeking are impulsive, fickle, excitable, quick-tempered and extravagant, while those scoring below average tend to be reflective, rigid, loyal, stoic, slow to anger and frugal.

About 15 percent of people in Israel, Europe and the United States carry the novelty-seeking form of the gene. But just why it would encourage novelty-seeking is still a mystery, Ebstein said.

About half the novelty-seeking variation between people is thought to be due to genes, and the gene in the study accounts for about one-fifth of this genetic component, he said.

The gene’s effect is too small to help an insurance company or prospective employer judge an applicant, said Dr. Jonathan Benjamin, lead author of the second study. And he said he believed they shouldn’t have access to such information.

Richard Coorsh, spokesman for the Health Insurance Association of America, said health insurers don’t intend to require any genetic testing for coverage. But if people who seek coverage as individuals rather than through a group plan get such tests on their own, the results would be part of their medical records that would be available to insurance companies, he said.

Ebstein’s results came from 124 adults in Israel who filled out a personality questionnaire and gave blood samples so their genes could be analyzed.

Ebstein’s findings were reproduced in a study of 315 Americans by Benjamin and colleagues at the National Institute of Mental Health and the National Cancer Institute in Bethesda, Md. Benjamin is now assistant director of psychiatry at Soroka Hospital in Beersheba, Israel.

Considering past failures in behavioral genetics, Benjamin wants more confirmation of their finding.

xxxx
How the gene works
This is how scientists say the gene works: Novelty seekers tend to have a particular variant of a gene that allows the brain to respond to dopamine, an essential chemical communications signal.
The gene encodes the instructions for the so-called D4 dopamine receptor, one of five receptors known to play a role in the brain’s response to dopamine. As it turns out, novelty seekers possess a version of the D4 receptor gene that is slightly longer than the receptor of more reserved and deliberate individuals.
In theory, the long gene generates a comparatively long receptor protein, and somehow that outsized receptor influences how the brain reacts to dopamine.
Dopamine is only one of many so-called neurotransmitters found coursing through the brain, sharing its chemical communications duties with such other renowned neurotransmitters as serotonin and norepinephrine. However, dopamine is the chemical most strongly linked to pleasure and sensation seeking.